48 Dr. G. E. Allan on 
resistance 1°93 B. A. ohms. A wide-mouthed compensating- 
coil was placed between the magnetometer and the scale. 
The two coils and the magnetometer were carried ona 
wooden stand provided with levelling-screws, the magnet- 
izing-coil being fixed on the stand, whilst the stand holding 
the compensating-coil was movable by means of a screw, and 
was held in position by brass springs. 
The magnetometer consisted of a small piece of steel spring, 
1 em. long, stuck on the back of a cross cut out of thin sheet 
copper. The cross held in front a mirror, 1 cm. iz diameter, 
which had been cut from a thin convex lens siivered on one 
side, and was suspended by a fine quartz fibre 30 ems. long, 
the needle hanging inside a block of bronze that served to 
damp its vibrations. The mirror had a focal length of 
1 metre, and cast the image of a cross-wire on a transparent 
scale at a distance of 175°5 cms. The arrangement of the 
apparatus, so as to allow the necessary readings and mani- 
pulations to be made by one observer, is shown in fig. 2, 
Fig. 2.—Diagram to show arrangement of apparatus. 
oD) 




CheEr7710 meter. 

to platinwm 

where F is the furnace and magnetizing solenoid and C the 
compensating-coil, M is the magnetometer with its lamp L 
and scale 8. The coil C, noaunelaves the disturbing effect of 

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ee i i 
